Lifting magnet



J. E. SEDERHOLM April 7, 1925.

LIFTING MAGNET Filed Ja, '7.t 1922 Shets-Sheet 2 JOHN DERRECK COEEZPEY, OLIVER, il',

all" @F'Flfn arrivino. ranennr.

v .ipplcation led vJanuary 7, i922. Serial No. 527,679.

To all fui/720m t 'may concern:

l lie it lrnown that l, loi "il a citizen of the UnitedStates, resident of Paul, in the county'of Ramsey and State of Minnesota, hare invented Vcertain new and useful n'iprovements in Lifting Magnets, of which the following is a'speciii cation.

rlhis invention relates to improvements in magnets designed for picking up .and inovi'ng from one place to another articles of iron or steel.

rihe principal objectjof my invention is to provide a lifting magnet havin A its winding divided or split up into a plurality of sections, making it possible to change the voltage of the current employed without re-winding the inagi'iet. Y

Another object of the invention is to provide for the operation of a lifting inagnet with currents of high voltages without -he employment of external resistanceV4 in the main circuit, as usually employed at the present time.k

1@ther objects of the invention will appear from the following detailed descrip tion taken in connection with the accompanying drawings in which,

r-Figure 1 is a perspective view of a lifting magnet embodying my invention;

ifigure 2 is u transverse vertical section online 2 2 of Figure 3,*looling in the direction of the arrow;

Figure 3 is a horizontal section on line 3-8 of Figure 2 looking in' the direction of vthe arrow, the coils being shown connected in series; Y

Figure l is a detailV plan view of the terminal box and a portion of the lifting magnet, the coils being shown connected in parallel;

Figure 5 is a detail section of the magnet shell, or case, looking from below, and showing a portion of the coils, and the means for holding the saine in place in the shell.

ln 'the drawings,l represents the magnet casing preferably formed of a single sheet of casting of circular forni, this casting constituting the magnetic circuit of the magnet. The outer surface of the magnet casing is preferably formed with a series of ribs 2 to increase the heat radiating surface. The top of .the casing is preferably l, i v, n. Snonnnonui,

provided with a series of lugs 3, 3, to-

the bottom of the casing. I provide with-y in the annular recess 9 a plurality of coils or windings. l have here shown two such coils, the inner being designated 10 and the outer 11. These coils are spaced apart and are held in position in said recess by a vseriesof straps 12, extending across the under side of the coils and secured in po-l sition by bolts 13, that extend through said straps and pass upward between the coils and are screwed into threaded recesses le in the upper part of the casing (Figure 2).

A non-magnetic coil shield plate15,1i refif erably provided upon its upper surface with a rubber gasket 16, is seated in shouldered recesses 17, 17, in the bottom of the casing surrounding the annular recess 9 (Figure 2).

fin outer annular pole shoe 18 is secured to the bottoni of the casing, outside of the annular recess, by bolts 19, and this shoe is preferably arranged to project inwardly7 a short distance beyond the wall of the recess so as to engage the outer edge of the non-magneticcoil shield plate 15. (Figure 2). The center of the. Vcasing 1 is preferably provided with a Ventilating' ope-ning 20. sinV inner circular pole shoe 21, having preferably a central Ventilating opening 22, coinciding with the opening 2O in the casing, is secured to the casing by suitable bolts 23, that pass through openings 2l in said pole shoe and correspond ing opening 25 in the casing.

The heads of the bolts 19 and 23 are preferably arranged in countersunk recesses in the pole shoes so as to leave said shoes with smooth under surfaces.

The pole shoe 21 preferably project-s slightly beyond the inner wall of the recess 9, thereby engaging the nonniagnetic coil shield plate 15, and holding this edge of the plate in position over the recess (Figure 2). An opening is formed through the top wall of the casing (Figures 2, f3 and 4r), and this opening forms a terminal box 26 through which connections may be made with the coils 10 and 11 within the casing. The terminal box 2G is provided ith a suitable cover 27 secured in position by bolts 28, and it has lugs 29 through which extend the connecting pins 30 to which the electric conclue tors 3l, 3l, are attached. I provide suitable connectors 2:52 between the pins 30 and the coil terminals Z, and also one or more connectors connecting said coils.

I may connect said coils in series, as illustrated in Figures l and 8 ot the drawings, v)r I may connect them in parallel as illustrated in Figure The terminal box cover 2T is preferably provided with an opening Se arranged to be closed by a threaded plug 35 (Figures 1 and l). After the parts are assembled, in the manner described, the entire space within the recess surrounding and below the coils may be iilled with pitch, 36, or other suitable material, that is melted and run in through the opening in the cover ot the terminal box.

,Vhile I have shown but two coils arranged within the recess in the casing a greater number of coils may be employed it desired.

By employing a plurality et coils, thereby splitting the winding of the magnet up into two or more sections, it is possible to change the voltage of the. magnet without re-winding the coil. The magnet may also be operated on high voltages without using external resistance in the main circuit as is usually done at the present time. lilith this arrangement it is possible to put a discharge resistance across each section ot winding, cach section being connected to the controller.

The high inductive potential set up when the circuit of the lifting magnet is broken, due to the great mass oi iron surrounding the coils, is, with my invention, divided up between the coils in my new design, making the breaking down strain 1/2, 1/3, or V, of the magnet using only one coil.

lilith this construction better ventilation is secured thus increasing the lifting capacity of the magnet without increasing its own weight.

lVith a duplex, triplex, or quadrupler; construction ot' coils, a row ot bolts should be inserted between each pair el: sections ol coils, with a suitable strap ett noirmagoetic material extending across all of the coils. This makes a very rugged and firm consti-auftion. Metallic spools such as hare heretofore been used are done away wth, as such spools make a magnet sluggish and tend to increase the temperature through eddy currents generated in the spool.

I do not limit myself to the use et two coils in the casing, as a greater number may be employed without departing .trom my invention, nor do I limit mysell' to the details of the construction herein disclosed as the same may be varied in many particulars without departing from my invention.

I claim as my invention:

l. In a device of the class described, the combination, with a circular, metallic magnet case, having an annular recess forme-:l in one face thereof, of a plurality et concentric coils arranged in said recess, an annular ring of insulating material between the coils, bolts passing up through said material into said casing with means thereon to retain the coils in said recess, means connecting said coils in series or in parallel, and inner and outer removable pole shoes secured upon the lower tace of said 2. In a device ol the class described, the combination, with a circular metallic magnet case having an annular recess `iomued in one face thereof, of a plurality ot concentric coils arranged in said recess, and :1 series ot straps extencing across said coils and below the same, bolts passing through said straps and between said coils and engaging openings in the upper wall of' said case.

In witness whereof, I have hereunto set my hand this 31st day of December, 1921.

JOHN E. SEDERI-IOLM.

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